Process for reconditioning used solutizer solutions



1 liit m arcane raocess roa nncorrro x SOiLlU'lEll sorm'rrons Allan i7. hlinon, San Francisco, and i'lrrla ii. lllavis, ilahland, ilalii... asslarnors to Shell hevelopment lflompany, San lrancisco, il'alii, a corporation oi Delaware l lo mrawina. application May 2?, ldlill, Serial No. name it iliaims. (ill. 252-1192) is concerned with a method io'r .treatina a contaminated solutiaer solution with a solid maenesium oride, whereby gums and resinous emulsitiers are removed.

Th aolutiaer process by means oi which mencal ans and other weah organic acids contained in sour hydrocarbon distillates, and more particularly in easoline distillates,, are extracted with aolutiaer solution, i. e. aqueous solutions oi allrali metal hydroxides containing solutiaers, is well lrnown The solutiaerprccess has been described, and the several compounds particularly suitable as aolutiaers have heen enumerated in a series oi natents and patent applications, as well as in the aeneral literature, tor erample, in the Yabron et al. ll no Patents arrears-anamoadhhltt areayao area-res hlththi h,lhlhdhh-dflllh,t 3ll2,2%3,79d-2,229,995; Refiner and ilatural iiasoe idanuiacturer, hiar lillil, panes ill to lit and March tiled. p ates '33 to id, industrial and Engineering Chemistry, vol. it, paces an to sea, February re ro, Chemical and hietalluraical ldnahneerine, vol. d7, panes "lit to tilt, liovemher lath, Uil and Gas Journal, vol. so, lilo. to, paces 55 to at, November 7!, rate, etc."

in principle, a aolntiaer solution could be used indefinitely hy continually reeeneratine it as by steam. in practice, however, solutions used a lone timetend to term relatively stable emulsions with the hydrocarhon'oll under treatme only due to eradual ace .61

helieved to he resinous substances which em "alone either reduce the throueh-put due to retarded eettlina or cause the carry-over oi valuahle solutlzer. Uoalescinc' entrained droplets by contact with nine steel wool or other solids may not always remedy the situation. it is in such solutions used continuously and tor a very lone, period in a solutiaer plant that our recondltio process is particularly useful.

e eract source and chemical composition oi the emulsifier are not mown. it appears to he a my material oi a resinous na. Possible sources oi it include cracked gasoline ieeds contal dissolved gums, oxidation or small amounts oi cracked easoline dissolved in the solution, oxidation oi portions oi solutizensolutlon such as alkyl phenols which may purposely iorm p oi the solutlzer solution or which may acculate in 'solutizer solutions when. cracked aasoline leeds are treated.

The object or this invention is to facilitate th treatment oi hydrocarbon distillates by means or solutizer solutions. another purpose is to decrease the costs of operation in solutizer plants by we a lzina or preventing losses of valuable solutizer which are sufiered when contaminated solutions must be discarded. Still another purpose is to decrease emulsion and foaming difiiculties in solutizer plants. A more particular purpose is to provide a method for the removal of resinous emulsifiers and troublesome solids from used solutizer solutions.

Our invention is based on the discovery that resinous emulsifiers which-accumulate in used solutiaer solutions may be removed by subjectin the said allraline solutizer solution to a'treatment with solid magnesium orlde, thereby rendering said solution clean and again suitable for use in I the solutiser process tor the extraction of mercaptans.

in carrying out our invention, a contaminated solutiaer solution containing a resinous emulsifier is subjected to a treatment with a solid adsorbent comprising magnesium oxide to adsorb resinous emulsifier and other troublesome impurities, and to form a suspension of solids in the solution. The solid adsorbent together with the adsorbed emulsifier are then separated, and the resulting clean solutlzer X solution is removed, ready to he reused.

The adsorbent may consist entirely of l'l/igO or maycontain different amounts-oi activated carhon; in eeneral, mixtures or Mei) containing a minor portion oi activa carbon are preferred. her, the adsorhent may be mixed with clays or inert solids such as other substantially water insoluble metal orides, etc.

By a contaminated solutizer solution we mean one contag an emulsifier which has slowly a d the regeneration treatment and which is in solution or, colloidally dispersed thereby caus' said solution to have a tendency to form ulsions which may be relatively Stable when it is mined witheasoline in the course of the treatment or to learn excessively when the spent solution is helna steam stripped thereby tax-1i the smooth operation of a solutizer plant.

The d activated carbon used as adsorbents in the process may be the ordinary commercial grades or these substances in powdered form. The particle oi the solid adsorbent is to be codered, the ability of the solid to adsorb as its tlcle size decreases. 0n the other lid,

uculties in separation may arise if the particle size is too small. It will usually be found satisfactory to use a powdered adsorbent of a fineness such that the larger portion of it passes through a 200 mesh screen.

The effectiveness of the removal of the undesirable contaminants is dependent on two factors: the concentration of alkali metal hydroxide in the contaminated solution and the amount of solid adsorbent which is added. The effectiveness of the treatment for a particular amount of adsorbent generally increases to a maximum as the dilution is increased, but the treatment of extremely diluted'solutions in general is not practical due to the cost of reconcentrating such solutions. On the other hand, if the concentration of alkali metal hydroxide is high, little improvement will in general be realized even when relatively large amounts of solid adsorbent are used.

Normally solutizer solutions after having been steam stripped are at least 2 normal with respect to alkali metal hydroxide. At the time the solution is treated with the adsorbent it should contain alkali metal hydroxide in a concentration, preferably below 2.5 normal and above 0.5 normal, concentration between 2.0 and 1.0 normal in general being most practical. Thus when startme out with a solutizer solution which contains alkali metal hydroxide in concentration of about 6 normal as is most usually used, it may be advantageous to carry out the treatment in a dilution of at least 3:1 water, preferably distilled water, to solutizer solution. The amount of solid adsorbent to be used may vary between 25% and by weight of the diluted solutizer solution.

In general, the greater the dilution the smaller will be the amount of adsorbent to be used.

Since the treatment is much less effective if the magnesium adsorbent is the slalred form, 1. e. Mg(OH)2, the unslalred form, i. e. MgO, should be used, and in order to avoid its slaking, the ad sorption should be carried out in a solution that is cold or at least one that is not heated substantially above normal room temperature.

The method of contacting the solution with the adsorbent should be one enabling intimate contact, so as to cause entrainment of the resinous emulsifier with the adsorbent and its separation from the cleansed solution. The adsorption may be carried out by mixing the powdered adsorbent dry or in the form of a slurry with the solution and separating the solid by settling, filtering, centrifuging, etc. Or else, we may percolate the solution through a bed of adsorbent in granular form. The first of these two methods is usually preferred. The contacting may be continuous, or batohwise, and may be resorted to whenever the emulsifier content has built up to proportions which under the particular conditions in the plant may prove unfavorable. The mixture should be agitated during treatment as by stirring.

The following explanation and examples illustrate the effectiveness of our treatment:

When solutizer solution and gasoline are passed in counter-current fiow through an extraction tower in which the aqueous phase is continuous, an emulsion of the oil-in-water type is formed which collects at the top of the solutizer solution. A similar type of emulsion can be formed by stirring solutizer solution and gasoline together, and a stirrer test was accordingly devised whereby small amounts of solutizer solution and gasoline could be caused to form an emulsion under controlled conditions, and the time of settling measured.

Example 1 A full-range cracked gasoline was stirred vigorously under the above controlled conditions with a contaminated aqueous solutizer solution containing potassium hydroxide 6 normal, potasslum isobutyrate 1.6 normal, and potassium phenolate .7 normal. The settling time (time necessary for the separation of the tWo phases) was eight hours. The separation was not clean, a rag remaining after settling. Another portion of the same contaminated solutizer solution was diluted with 3 volumes of water and contacted with about 0.75 by weight (based on diluted solutizer solution) of powdered magnesium oxide. The mixture was centrifuged for fifteen minutes at fifteen hundred R. P. IVL, filtered through a sintered glass filter and then reconcentrated by boiling. The reconcentrated solution was then stirred with the same full. range cracked gasoline and the settling time was found to have dropped I to twelve minutes. The phases separated cleanly The above contaminated diluted solutizer solution was treated with a solid adsorbent comprising .5% by weight magnesium oxide and 25% by weight activated carbon. The treated solution was filtered and reconcentrated and was then agitated with the same cracked gasoline and under the conditions of Example 1.

The settling time was in this case reduced to about nine minutes, with a clean break,

We claim as our invention:

1. In a process for reconditioning an aqueous alkali metal hydroxide solution containing a solubility promoter for mercaptans and a resinous emulsifier accumulated in the course of treating hydrocarbon distillates with said solution, the steps comprising contacting said solution with a small amount of a solid adsorbent comprising magnesium oxide, under conditions to entrain the resinous emulsifier with the adsorbent, and separating said adsorbent containing entrained emulsifier from said solution, the latter having retained said solubility promoter.

2. The process of claim 1 wherein the concentration of the alkali metal hydroxide solution is between 2.5N and .5N.

3. The proces of claim 1 wherein the concentration of the alkali metal hydroxide solution is between 2.0M and LON.

l. The process of claim 1 in which the said amount is between 25% and 1.5% by weight of said solution.

5. In a process for reconditioning an aqueous alrali metal hydroxide solution containing a solubility promoter for mercaptans and a resinous emulsifier accumulated in the course of treating hydrocarbon distillate with said solution, the steps comprising contacting said solution with a small amount of a solid adsorbent comprising magnesium oxide and activated carbon, under conditions to entrain the resinous emulsifier with the adsorbent and separating said adsorbent containing entrained emulsifier from said solution, the latter having retained said solubility promoter.

6. The process of claim 5 wherein the solid adsorbent comprises a major proportion of MgO and a minor proportion of activated carbon.

7. In a process for reconditioning an aqueous solution of alkali metal hydroxide having a concentration above 2.5N and containing a solubility promoter for mercaptans and a resinous emulsifier accumulated in the course of treating hydrocarbon distillates with said solution, the steps comprising diluting said solution with water to a. concentration ofthe alkali metal hydroxide between 2.5 and .5N, contacting resulting diluted aqueous solution with a small amount of a solid adsorbent comprising magnesium oxide, under conditions to entrain thefresinous emulsifier with the adsorbent, and separating said adsorbent containing entrained emulsifier from said soluconcentration of about 6N and containing a solution, the latter having retained said solubility promoter.

8. The process of claim 7 wherein the water of dilution is distilled water. 9. The process of claini wherein the metal hydroxide content of the concentrated solution is about 6N, and that of the diluted solution is about 1.5N.

bility promoter for mercaptans and a resinous emulsifier accumulated in the course of treating hydrocarbon distillates with said solution, the steps comprising diluting said solution with about 3 volumes of distilled water, and contacting the resulting diluted solution with .25 to 1.5% by weight of a solid adsorbent comprising magnesium oxide, under conditions to entrain the resinous-emulsifier with the adsorbent, and separating said adsorbent containing entrained emulsifler from said solution, the latter having retained said solubility promoter.

ALAN C. NDKON. ORRIS L. DAVIS. 

